I have searched and looked thru several threads regarding gas mileage, and also did some digging on the net.

From what I have read here and on the net, the gas mileage on the 4.7's isnt the greatest to begin with. I didnt buy the truck for gas mileage, but would like to get the most out of it. It is an 04 SLT 4.7L extended cab.

What I have done so far...

I have replaced the plugs, I use 89 octane fuel as its the lowest octane by me, made sure the air pressure is set to factory spec of 35 PSI, factory size tires. I dont have a lead foot, I drive casually. I ran Sea foam thru the fuel system and thru the Brake booster Vacuum line to help clean up some carbon.

The most I have gotten out of the tank with some highway and mainly city driving is a little over 200 miles to the tank. my last tank of gas got me a little over 100 miles city driving.

I Just got brand new tires (factory size)
No codes. I ran my scanner and there are no errors.
Cat looks good, exhaust fumes dont smell.
Brakes are new, wheel bearings spin freely.
Front suspension is all tight and the alignment is dead on. (just had that checked on Tuesday.

The only thing I have heard is the MAP sensor could be going bad but not enough set to set a light. Would that deminish my MPG?

Is this normal?? Or is there something Im over looking? Any help is appreciated.

 

I'll telly ou right now, I have the 3.9 V6, and I'm only getting 13.0 right now. In the summer I was getting 14.5 and no more. Granted my foot is a little on the heavy side.

Once I get my lighting finished so I can see worth a d@mn at night, my next task is the O2 sensors. I replaced my MAP when i put my custom-ground V8 throttle body on it, and I did plugs this week. All I have left is the distributor cap/rotor/coil/whatever else is down that line, the injectors, and the O2's. The injectors are last on my list because of cost and complexity (and I really dont like the idea of dealing with fuel lines and O rings after User's fire).

 

I can understand a drop in MPG during the colder months, especiallly in Illinois. The thing that boggles me is my other truck which is a 04 Silverado SS with a 6.0, more power, all wheel drive, and weighs more gets better mileage.

 

There is something wrong. You should be getting more then 100 miles a tank in the city with the 4.7, cold weather will not be a huge difference yes it stays in open loop for a tad longer dumping fuel, but honestly maybe 10mile difference from winter and summer. Nothing to be worried about really.

I would say you need to do some type of tune up. I know the 4.7s have coil packs, so its going to be a tad bit more expensive then the guys with dist.

Run some sea foam in the gas tank to clean out the injectors, also run some through the combustion chambers (by using a vacuum hose to suck it out of the can) and let it do its magic.

I would also do a tune up, coils, plugs, ect.

100 miles a tank sounds like you might have some type of fuel leak. If you say its not running rich. I would pull some plugs and see if they are fouled.

If you have been driving like this and its dumping fuel the cats are shot and probably the o2s also, causing an even worse problem.

 

The Dodge Service Manual says the MAP sensor is the number one contributor to the fuel pulse width. It's hard to know what to do because correct operation of the sensor depends on the barometric pressure and the altitude where you live. On my 3.9 the MAP was reading 1.3 volts on the center wire with the engine idling. Here in central Florida the MAP should have been reading somewhere around 1.5. I replaced it and it helped my power and MPG did improve somewhat, but not a whole lot.

Check out this thread, There's a lot of good info on it about the MAP sensor.

https://dodgeforum.com/forum/2nd-gen...er-solved.html

Jimmy

 

MAP sensor sounds like a culprit(never done mine), or throttle body cleaning. I did plugs after 55K and noticed a great improvment...peppy and MPG. Just NGKs..nothin fancy. I get between 15-18(on the console) which is like 13-17 ODO/gallons.

I am running an 04 Ext Cab with a 4.7...5spd. I do a lot of engine braking as well....I really should stop...brakes are cheaper than gas!! lol...good luck!

 

He said he already did that...

 

I just replaced the plugs 200 miles ago, and ran sea foam in the tank and the Brake booster line. If the coil packs were going bad the truck would be getting a mis fire code, and running rough. It isnt doing either.

If the 02's were shot I would get a check engine light. The cats are fine, no glowing,rattling, the exhaust fumes arent harsh.

 

I have a 98 5.2 4x4 auto I get 130 miles on a half of a tank. Best I got on a tank I think was like 250 and that was running it almost empty

 

thats what I'm getting, about 235-250 per tank, with a V6 and heavy foot.